The compacted, bentonite-based absorbents of this invention may be used for a wide variety of liquid absorbing applications. The absorbents are particularly well suited for use as animal litters. A search of the prior art located the following patents relating to animal litters.
______________________________________ U.S. Pat. No. DATE OF PATENT PATENTEE ______________________________________ 2,649,759 8/1953 Gibbs 3,286,691 11/1966 McFadden 3,765,371 10/1973 Fisher 4,009,684 3/1977 Kliment et al. 4,275,684 6/1981 Kramer etr al. 4,315,761 2/1982 Larson et al. 4,343,751 8/1982 Kumar 4,395,357 7/1983 Kramer et al. 4,409,925 10/1983 Brundett et al. 4,459,368 7/1984 Jaffee et al. 4,494,481 1/1985 Rodriguez et al. 4,494,482 1/1985 Arnold 4,506,628 3/1985 Stockel 4,532,890 8/1985 Ohki et al. 4,570,573 2/1986 Lohman 4,591,581 5/1986 Crampton et al. 4,638,763 1/1987 Greenberg 4,641,605 2/1987 Gordon 4,657,881 4/1987 Crampton et al. 4,671,168 6/1987 Smith 4,685,420 8/1987 Stuart 4,686,937 8/1987 Rosenfeld 4,844,010 7/1989 Ducharme et al. 5,000,115 3/1991 Hughes 5,062,383 11/1991 Nelson 5,129,365 Hughes 5,317,990 6/1994 Hughes 5,452,684 9/1995 Elazier-Davis et al. Re. 33,983 7/1992 Hughes ______________________________________ FOREIGN DATE OF PATENT NO. PATENT COUNTRY ______________________________________ 87001 8/1913 EPO 0087001 8/1983 EPO 0242478 10/1987 EPO 0378421 7/1990 EPO 0424001 4/1991 EPO 3620447A1 12/1987 Fed. Rep. Germany 58-009626 1/1983 Japan 0094043 5/1985 Japan 63-219323A 3/1987 Japan 3044823 2/1988 Japan 3185323 7/1988 Japan 1191626 8/1989 Japan 58009626 7/1981 Japan 00094043 5/1985 Japan 1119127 6/1986 Japan 239932 10/1987 Japan 2239932 10/1987 Japan 1191626 1/1988 Japan 63-44822 2/1988 Japan 44823 2/1988 Japan 3044822 2/1988 Japan 3044823 2/1988 Japan 185323 7/1988 Japan 3185323 7/1988 Japan 3219323 9/1988 Japan ______________________________________
The Examiner's attention is specifically directed to the following patents relating to bentonite-containing animal litters (and to the additional prior art listed therein): U.S. Pat. Nos.: 4,591,581; 4,657,881; 5,000,115; 5,129,365; 5,317,990; 5,452,684; and Re. 33,983 (hereinafter the "Hughes Patents"). Further, the foreign patents listed above (and other prior) may be located in the last mentioned patent prosecution histories.
The prior art contains numerous patents on animal litters of various types. The use of clumping animal litters from natural clays has recently been developed and is now a well established product widely used by consumers. Although consumers have used a wide variety of clay and non-clay materials with various additives to provide animal litters, the primary growth market for animal litters is in the area known as "clumping litters". The most widely used and best known material used for clumping litters is shown and claimed in the Hughes Patents, including U.S. Pat. No. Re. 33,983, i.e., water-swellable bentonites. Bentonite clays have been routinely mined, dried, ground into a useable particle size distribution and sold (optionally with fragrance bactericide and other additives) for use in animal litter boxes, in particular, for use in feline litter boxes (a.k.a. cats). Although the use of water-swellable bentonite materials as animal litter is well established and has grown in the last several years to represent a significant percentage of all animal litter sold, the use of such water-swellable bentonite materials has undergone little change or improvement over the last several years. Manufacturers have provided variations in fragrance, appearance, particle size and various other selected additives in an attempt to provide product differentiation to consumers in their bentonite-based litter products, but no significant changes in animal litter have been observed. Although consumers recognize these marketing differences as between animal litters, there have been no significant improvements in the processing of bentonite clays for use in animal litters so as to substantially improve the performance and use of bentonite-containing animal litters.
The manufacturing process as for bentonite-based litters generally involves a drying, grinding and sizing process for mined, field dried bentonite pursuant to which a ground bentonite product is put into containers and then sold to consumers. Several patents have claimed the use of bentonite-containing clays for use as animal litters. The several patents issued to John Hughes (U.S. Pat. Nos.: 5,000,115, 5,129,365, 5,317,990 5,452,684; and Re. 33,983 of U.S. Pat. No. 5,000,115): the "Hughes Patents") disclose the use of a "non-compacted" water-swellable bentonite clay for use as an animal dross absorbent. The patentee discusses at great length the need to use a "non-compacted" bentonite and bases this discussion on the disclosure of U.S. Pat. No. 4,657,881 and the testing of samples prepared based upon the disclosure of U.S. Pat. No. 4,657,881. The patentee states that compacted clays are very adherent to animal's paws and fur after wetting. (The patentee relies on this statement as a basis for distinguishing the disclosure of U.S. Pat. No. 4,657,881 which does not relate to compacted bentonite but actually discloses the compaction of non-swelling clays.) At column 11, lines 28 to 47 of U.S. Pat. No. 5,317,990, the patentee demonstrates that a compacted mixture of sodium bentonite and calcium bentonite provided a granular litter that was slow to absorb a NaCl solution, had puddling, formed thin, pancake shaped clay masses and was very sticky. The patentee states at column 10, lines 65 et seq. that the compacted bentonite clay was compacted by compression in a tablet machine (as disclosed in U.S. Pat. No. 4,657,881 (Crampton, et al.), and then ground and sized to remove all particles below 710 microns and greater than 4 mm. The tablet machine in Crampton applied a pressure of 5 KN/sq cm (approximately 2860 pounds per lineal inch gauge). Accordingly, U.S. Pat. No. 5,317,990 teaches that compacted sodium and calcium bentonite are unsuitable for animal litters. Apparently, the patentee used a wide particle size distribution of the bentonite mixture that was compacted for testing. The patentee of U.S. Pat. No. 5,317,990 is also the patentee of Re. 33,983 which discloses and claims the use of a water-swellable bentonite clay having a particle size from about 50 microns to about 3350 microns and having a sufficient amount of fine particles so that upon wetting, a substantial quantity of the clay will agglomerate. The patentee discloses the water-swellable bentonite to have this distribution of large particles as a result of grinding and sizing naturally occurring, mined bentonite. The patentee does not discuss compacted water-swellable bentonite clays or the use of bentonite fines to form an animal litter.
The prior art further discloses (U.S. Pat. No. 4,657,881) that a water-swellable bentonite compacted at a pressure of 5 KN/cm.sup.2 (2860 lbs/lineal inch) is unsuitable for use as a clumping animal litter. Further, U.S. Pat. No. 4,657,881 discloses that formation of compacted clays for use as a litter should not include more than 10 percent by weight of any naturally or synthetic swelling clay additive (see: column 3, lines 46 to 57 whereat the patentee states the amount of "additive" which can be used. Bentonite is identified in column 2, lines 66 to 68 as an "additive"). What is clear from the above discussion of the prior art on the use of bentonite-containing material is the teaching that compacted water-swellable bentonite clays are not suitable for animal litters. The instant invention demonstrates that the prior art teachings failed to appreciate the benefits of compacted water-swellable bentonite as an animal litter owing to use of low compacting pressures, incorrect assumptions (without testing) on the nature of compacted water-swellable bentonite and failure to appreciate the use of feline urine in evaluating the use of compacted water-swellable bentonite as a feline animal litter.
U.S. Pat. No. 5,452,684 (Sep. 26, 1995) discloses a process for extruding smectite clay (bentonite-containing clays) wherein the smectite clay is shear extruded with large amounts of water and/or an adhesive binder. The patentees disclose that by use of an extrusion process that them is an increase in the overall clump strength as a result of a shearing process which occurs during extrusion through a die opening. The patentees state that the shear extrusion process provides an alignment of the clay platelets as a result of the extrusion process which substantially increases the strength of the final clumps. The improvement in the clumping strength is not stated to result in any change of the absorbency of the material. The patentees state at column 8, lines 22 to 30 that:
"Generally the moisture of the clay should be in the range of about 20% to about 45% based on the dry weight of the smectite clay when the clay is extruded. The extrusion is more efficacious when done on rehydrated smectite clays rather than crude undried clay. If the clay is too dry it would be forced through the die openings in a powdery form without sufficient platelet alignment, and, therefore insufficient improvement in clump strength."
In addition, the patentees state that it is preferred to provide, in addition to an extremely high water content bentonite, an adhesive in an amount from about 0.025% to less than about 0.1% by weight. The preferred adhesive is carboxymethyl cellulose. As noted above, the water content is preferably between about 20% and about 45% and preferably an adhesive is employed to provide the animal litter. Further, the patentees discuss at column 9, lines 25 et seq., that it is preferred to use a bentonite-containing material which has a typical and preferred particle size in the range of about 10 microns to about 200 microns and preferably less than about 100 microns. The examples of U.S. Pat. No. 5,452,684 do not disclose or allege to have changed the overall absorbency of the bentonite-containing animal litter.
The instant invention employs bentonite fines to produce an improved animal litter. The litter has both improved absorbency for feline urine and improved dry clump strength. Bentonite fines have previously been used as components of drilling muds, cosmetics and for iron ore pelletizing ("IOP"). Fines (very small particles) also often result from the manufacturing of animal litter using bentonite and have generally been discarded as landfill materials or reused by addition of large amounts of water, processed by pin-mixing and then redried, sized and reprocessed. This discarding or pin-mixing of the bentonite fines is costly and can result in a significant percentage of the bentonite from not being used as final product. This increases the cost of the animal litter to consumers. As aforementioned, manufacturers have sought to recover these fines through a process called "pin mixing" pursuant to which large amounts of water are added to the fines and the material is pin mixed under low pressures and then dried, ground and sized. This addition of large amounts of water up to 30% by weight (based on the total weight of the bentonite) is expensive in view of the significant additional energy cost of water removal.
The instant invention relates to absorbents containing compacted bentonite-containing particles which show improved absorbency and dry clump strength when used as absorbents.